Covalent Triazine Frameworks Incorporating Charged Polypyrrole Channels for High-Performance Lithium-Sulfur Batteries

Abstract

Covalent triazine frameworks (CTFs) have emerged as promising electrode materials for lithium-sulfur (Li-S) batteries owing to their pristine pyrdinic sites, conjugated backbone and ability to stabilize remarkable sulfur contents. Following the first synthesis of sulfur-CTFs under catalyst and solvent-free reaction conditions[1], new synthetic strategies have been extensively investigated to improve CTFs properties for Li-S batteries applications. Further upgrading for CTFs was introduced to achieve extremely high sulfur contents CTFs via employing nucleophilic aromatic substitution reaction (SNAr) between perfluoroaryl units and elemental sulfur.[2] However, the previous (SNAr) approach possessed immense sulfur conent up to 82%, it is challenging to endure high ionic and electronic conductivity with mitigation of Li-polysulfide (Li-PS) shuttling. These fatal problems limit their cycling performance at high active mass loadings. In an effort to tackle the previously mentioned problems, a new approach incorporates the integration of one-dimensional charged conducting polymers with a two-dimensional covalent triazine framework in the presence of elemental sulfur.[3] Noticeably, the addition of charged conducting polymers triggers a 3D nanochannel formation in the CTF framework with high-affinity anchoring sites towards Li-PS while achieving decent ionic and electronic conductivity. The resulting polymers showed significantly improved ionic , electronic conductivities and high sulfur loadings. Because of these remarkable properties, we are able to obtain exceptional electrochemical performance at high mass loading of 3 mg sulfur per cm2 with a specific capacity of 1275.2 mAh g−1 at 0.05C.